Copper nickel alloys



United States Patent 3,399,057 COPPER NICKEL ALLOYS William Henry Richardson, Datchet, and Douglas Brown, Slough, England, assignors to Langley Alloys Limited, Slough, England, a British company No Drawing. Continuation-impart of application Ser. No. 627,642, Apr. 3, 1967. This application Feb. 20, 1968, Ser. No. 707,302

8 Claims. (Cl. 75159) ABSTRACT OF THE DISCLOSURE A cupro-nickel alloy having high strength, high ductility and excellent resistance to corrosion and sea water, and a magnetic permeability of below 1.1 having the followin compositions by weight: nickel, 1532%; aluminium, 1.53%; manganese, 4-6%; iron, .5-2%; balancecopper. The cupro-nickel alloy may also contain up to 5% chromium, up to 3% columbium and up to 3% silicon.

This invention relates to copper-nickel alloys and in particular to alloys containing maganese, aluminium and iron and is a continuation-impart of application Ser. No. 627,642, filed Apr. 3, 1967, now abandoned, which in turn is a continuation-in-part of application Ser. No. 362,454 filed Apr. 24, 1964, now abandoned.

An object of this invention is to produce cupro-nickel alloys having a magnetic permeability below 1.1 and which are highly resistant to corrosion by sea water and possess a high strength combined with excellent ductility and resistance to shock as measured by the Izod or Charpy Impact Valuea combination of properties much sought after in modern marine engineering practice.

Another object of this invention is to produce alloys which are easily hot worked, e.g. by rolling, forging or extrusion and which do not require critical control of the hot working temperature. Such alloys are in consequence of this, readily forgeable in, for example marine forge shops or repair shops where the control of the forging conditions may be considered inadequate for the forging of many other alloys of this nature.

A further object of this invention is to produce alloys of the type described above which although amenable to precipitation hardening heat treatments, do not necessarily require any heat-treatment, in order to achieve the combination of corrosion resistance, low magnetic permeability, high yield strength, high tensile strength, good ductility and high Izod Impact Value-another factor of importance when components in this alloy are required to be produced in inadequately equipped workshops.

A further object of the invention is to produce alloys which after hot working possess a combination of properties which may be still further enhanced by a subsequent precipitation hardening treatment.

For many years cupro-nickels (copper-nickel alloys containing up to about 40% nickel) have been regarded as the most suitable types of alloy for handling many corrosive liquids and, in particular sea water, and they have been extensively used for items such as condenser tubes.

Considerable research has been carried out with a view to improving still further the properties and, in particular, the corrosion resistance of these alloys.

However, the cupro-nickels used to date are generally of comparatively low strength although possessing extremely good ductility.

The following is a typical example of the mechanical properties of a standard alloy composed of copper, 30% nickel, after hot working and annealing:

EXAMPLE A Proof stress (0.5%) tons/sq.inch 10 Tensile strength tons/sq.inch 28 Elongation percent 45 Izod Value ft. lbs.--

There is now a growing demand for materials of this type which have the ability to withstand much higher stresses in service and consequently must possess higher strength and, in particular, appreciably higher yield strength or proof stress values, although the ability to withstand shock loads must not be too greatly reduced and hence the required alloys must retain a high degree of ductility particularly as measured by the Izod Impact Value.

The beneficial effects of aluminium as a strengthening agent in cupro-nickels has also been known for some considerable time and one of the highest strength alloys in this series is known as Hidurax (registered trade mark) Specialthe typical composition of which is as follows:

Copperremainder.

The alloy of Example B possesses the following mechanical properties in the hot rolled condition:

Proof stress (0.1%) tons/sq.inch 42.4 Tensile strength tons/sq.inch. 58.4 Elongation percent 13.5 Izod Value ft. lbs." 10

It will be noted that the alloy, Example B, possesses a proof stress and tensile strength far higher than the alloy of Example A, but the ductility as measured by elongation and Izod Impact Value is appreciably lower.

Hidurax Special responds to precipitation hardening, and because of this the ductility is reduced still further if the alloy is heated within the Precipitation Hardening range 400 C.600 C. and consequently it is not considered suitable for services within this range of temperature, particularly if subjected to shock loading. This embrittlement at elevated temperatures may also impair the Weldability of the alloy.

In the past, it has been considered that in order to achieve the best combination of properties in such copper-nickel-aluminium alloys, the ratio of nickel to aluminium should be in the region of 5:1.

It has now been found that the aluminium content should never exceed a value determined by this ratio and that increasing this ratio still further so that the aluminium content is less than one-sixth of the nickel content, results in an alloy possessing considerably higher ductility, as measured by elongation and Izod Impact Value although the proof stress and tensile strength are only slightly reduced if the nickel and aluminium contents are correctly selected, as shown by the following Example 1.

Balance substantially all copper.

3 4 MECHANICAL PROPERTIES WHEN HOT ROLLED Alloys according to this invention, i.e. containing be- FROM THE TEMPERATURE RANGE 1000 C. tween 1.5% and 3.0% aluminium, possess far superior 1050 C. proof stress and tensile strength in the hot worked condition without resorting to further heat treatment.

g i (08%) i3" Such alloys containing between 1.5 and 2.1% alum- Efnsle.strengt 0 Sig inium possess an excellent combination of proof stress,

ongauon f lb 30 tensile strength, ductility and Izod Impact Value as shown value by Examples 6, 7, s, 9, and 10 on Table III, this combi- Therefere the present invention p s a p nation of properties being achieved by Self-Precipitanickel having a nickel Content in the ge of 0 10 tion Hardening which takes place during cooling from 32% and an aluminium content in the range of 1.5 to th hot o ki g o rati 3.0% and less than one-sixth of the nickel content. Alloys within these limits of aluminium content may,

A further improvement in the mechanical Properties if considered necessary, be subjected to a further precipi- Of Snell alloys has now been effected y making a tation hardening treatment following the hot working op- Siantial addition of manganese Y this means it is 15 oration which results in a further substantial increase in Possible to Produce alloys in the hot Worked Condition proof stress and tensile strength (compares Tables III and Possessing excellent Combination of Proof stress, V below which show a series of alloys of the same composile strength, ductility and Izod Impact Value, but in itio difie tl t t d), order to achieve this, the manganese content must be Increasing the aluminium content still further has the controlled between 4% and 6% and the manganese c011- eflfect of increasing the degree of Self-Precipitation tent must be less than one half of the nickel content, and Hardening during nat l as opposed to induced cooling is preferably less than one-third of the nickel content. f om the not working process with a resulting further in- The use Of manganese n alloys of this type is not uncrease in proof stress and tensile strength, and Examples known, but examples of such alloys have usu y 011- 11, 12, 13 and 14 in Table III show the properties which tainted more than 9% manganese With the manganese and have been obtained on the rolled bar produced from alnickel contents being present in substantially equal proloys containing bet e n 2,1 and 3,0% aluminium without portions, and these known alloys have always to be S resorting to further heat treatment. It will be noted that jected to heat treatment if adequate strength is to be in ll a e the 0.1% proof stress in this condition is achieved. greater than 40 tons/sq. inch.

Th following Table I shows the Properties of two However, because of the high degree of Self-Precipialloys, the first according to the present invention, the tationv Hardening which takes place during natural coolother of similar composition with the exception that the ing from the hot working operation, when the alloy conmanganese content is 10.35% and m e n f e tains between 2.1 and 3.0% aluminium, they show little nickel content. response to subsequent precipitation hardening.

It will be seen that the proof stress and tensile strength Alloys falling within this range of aluminium content of the high manganese are considerably less t a therefore, should on no account be subjected to further those obtained on the alloy according to this invention, precipitation hardening since this results in only a very in spite of the fact that the rolled bar was produced in slight increase in proof stress, but may result in apprecian identical manner. able reduction in the Izod Impact Value, as will be obvi- TABLE I 0.1% Ultimate Proof Tensile Izod Example Ni, Al, Mn, Fe, Condition Stress, Strength, Elong., Impact Percent Percent Percent Percent Tons, Tons] Percent Value, sq. in. sq. in. it./lbs.

2 18. 2 1. 86 4. 77 1.32 1' Sq. hot rolled bar. NOT heat treated 29. 6 45. 6 30 70 a 16.9 1.89 10. 35 1.01 -...do 17.6 35.2 30 107 Balance substantially copper The aluminium content of alloys according to this inous from the results of precipitation hardening Examvention is particularly important since this determines the ples 20, 21, 22 and 23 shown in Table V. degree of precipitation hardening occurring during cooling Alloys ac rdi t thi i ti may b m lt d i from the hot working process. It consequently determines many types of melting furnace although it is an advantage the mechanical properties of the hot worked product and of the preferred alloys, i.e. those containing 15-20% in order to achieve the object of this invention it is imnickel that they are readily melted in fuel fired crucible portant that the aluminium content should be controlled furnaces, although of course they may be melted in many within the range of 1.5 to 3.0%. other types of furnace such as high frequency or low fre- In the aforementioned known alloys of copper-nickelquency induction electric furnaces. aluminium-manganese and iron, the published data dis- When all the ingredients are thoroughly alloyed and closes alloys containing 0.5%, 1.0% and 1.5% aluminium. the molten alloy has been heated to the necessary casting It has been found that alloys containing low proportemperature, it is ready for casting into suitable moulds tions of aluminium do not develop the required proof for subsequent hot working. stress and tensile strength in the hot worked condition. Alternatively, the molten alloy may be deoxidized with Table II shows the properties of two allows containing an addition of up to 0.25 oz. of lithium per 100 lb. of 1.34% aluminium and 1.17% aluminium, and hence outmolten alloy. This addition not only has the effect of proside the scope of this invention. ducing a high quality cast billet but also promotes im These two alloys which fall outside the scope of this proved weldability in the finished wrought products. The invention possess very inferior proof stress and tensile molten alloy may be cast into billets by any conventional strength. method but the preferred technique is to cast these billets TABLE II 0.1% Ultimate Izod Ni, Al, Mn, Fe, Proof Tensile El0ng., Impact Example Percent Percent Percent Percent Condition Stress, Strength, Percent Value, Tons/ Tons/ it./lbs. sq. in. sq. in.

4 16. 5 1134 4. 50 1. 4O 1' sq. hot rolled bar. NOT heat treatod. 18.0 36. 5 51 113 5 17.4 1.17 4.90 0.70 .do 18.5 3st 2 49 Balance substantially all copper.

by the Durville method, referred to on page 5 of the Metals Handbook 1948 published by the American Society for Metals of Cleveland, Ohio (see also the article by P. H. G. Durville entitled Still Casting of Metals Amer. Inst. Min. Met. Eng. Proc. Inst, Metals Div. 1927, 343

This non-turbulentmethod of casting billets is particularly desirable for an alloy of this type since it ensures freedom from aluminium oxide inclusions which may be formed by more turbulent methods of casting.

Billets free from aluminium oxide-inclusions are also readily obtained by utilizing the continuous or semicontinuous casting processes.

Unlike many other copper-nickel alloys and in particular those containing more than 9.0% manganese, the alloys according to this invention are readily hot worked by rolling, forging, extrusion or any other hot working process over the wide temperature range 900 C.- 1040" C.

After such hot working, alloys according to this invenof 75.0% and the mechanical properties obtained without any further heat treatment were as follows:

The majority of known copper-nickel alloys are susceptible to sulphur embrittlement when re-heated in furnaces fired by fuels of high sulphur content and, come quently, special reheating equipment is necessary for the successful forging of such alloys.

It'has been found that alloys according to this invention are not susceptible to such sulphur embrittlement as demonstrated by the following example.

tion possess the des1red combmation of mechanical prop- A 3" dia. section of rolled bar was heated 1n an 011 erties without the necessity for solution treatment and fired furnace at a temperature of 950l000 C. for a precipitation hardening as shown by the examples given penod of 8 hours. The sulphur content of the fuel oil bein the following Table III. mg 3.2% by we1ghtmax1mum.

TABLE III 0.1% Ultimate Izod Ni, Al, Mn, Fe, Proof Tensile Elong., Impact Example Percent Percent Percent Percent Cond1t1on Stress, Strength, Percent Value,

Tons/ Tons/ ft./lbs.

sq. 111. sq. 1n.

17. 3 1. 59 4. 87 1.14 Hot rolled bar. NOT heat treated s4. 4 45. 4 29 50 23.8 1. 55 4. 4 0.80 do 28.8 45. 0 109 19. 0 1. 75 4. 25 0.80 29. 4 45. 6 33 88 29. 2 1.81 5. 0 1.01 25. 2 41. 42 103 18.2 1. 86 4. 77 1. 32 29. 6 45. e e9 17. 1 2. 22 5. 1. 11 40. 5 57. 5 24 27 19. 5 2. 32 4.55 1.0 43. 0 57. 5 20 39 23. 1 2. 37 4. 0. 88 43. 2 59. 2 21 32 27. 5 2.81 4. 55 0. 95 do 48.0 54. 4 18 17.5

Unlike other :cupro-nickel' alloys and in particular those containing more than 6% manganese which require critical control of the hot working temperature, the alloys according to this invention can be successfully forged without the necessity for close temperature control and in fact the judgement of temperature by eye is sutficient to achieve an excellent combination of properties in the finished product.

The following table is a typical example of the properties which have been obtained by forging from 2 dia. to 1" sq. The forging being commenced respectively at 1040 C., 1000 C., 950 C. and 900 C.

0.1% Tensile Izod Forging Proof Strength, Elong, Impact Temperature, Stress, Tons/sq. Percent B.H.N. Value,

0. Tons] in. ft./lbs

sq. in.

It will be noted that the proof stress in all cases was 25 tons/ sq. inch or more but the most remarkable feature of these examples is the excellent consistency of the Izod Impact Value; all values lying between 62 ft. lbs. and 70 ft. lbs.

As further proof of the excellent behaviour of alloys according to this invention when forged under conditions of inadequate control, the following examples demonstrate that the percentage reduction in area during the forging operation, has little effect on the properties of the final forged product.

Two lengths of a 4 /2" dia. billet were reheated to 1000 C. Having attained the temperature, one length was forged to 3" sq., a reduction in area of 44.0%, and the second length was forged to 2" sq. a reduction in area The balance is substantially all Copper in all Examples 6 to 14.

Proof stress (0.1%) tons/sq. inch 25.0

Tensile strength tons/sq. inch 42.5 Elongation percent 42.0

Izod Impact value, 51.5, 48.5, 45.5 ft. lbs.

The fact that the material did not crack after prolonged heating at its forging temperature demonstrates that alloys according to this invention are not susceptible to sulphur embrittlement. The absence of any embrittlement is also confirmed by the good tensile and impact properties.

The above examples clearly demonstrate that alloys according to this invention can be readily forged in a variety of conditions of temperature, furnace atmosphere, etc., whilst still achieving an excellent combination of properties without resorting to further heat-treatment.

It is however an established fact that copper-nickelmanganese-aluminium alloys are amenable to precipitation hardening, i.e. they may be softened by heating to a temperature in excess of 750 C. followed by quenching or rapid cooling, and subsequently hardened or strengthened by reheating to a temperature in the range 300 C.- 600 C.

However, it is only by controlling the composition in accordance with this invention that such alloys will become Self-Precipitation Hardening during natural as opposed to induced cooling from the hot working process. The degree of such Self-Precipitation Hardening will of course be dependent on the rate of cooling and hence on the section of the finished product. But in the case of a1- loys according to this invention, it has now been found that the effect of such rate of cooling is comp ratively small and if the alloy is produced exactly in accordance with this invention, an excellent combination of mechanical properties can be achieved in hot worked products of a very wide range of cross section as demonstrated by the following Table IV.

A most important feature of these examples is the fact that the proof stress shows no tendency to decrease with increasing section. This characteristic is invaluable to the designer of marine engineering equipment, since the majority of high strength corrosion resistant alloys available hitherto possess increasingly inferior tensile properties as the cross sectional area increases and the designer must therefore increase the cross section of his components still further to allow for such reduction in strength.

Alloys according to this invention do not suffer this serious disadvantage.

Although these alloys possess an excellent combination of mechanical properties described above in the hot worked condition without the necessity for solution treatment and/or precipitation hardening, they may in certain circumstances be subjected to a precipitation hardening heat-treatment in order to effect a further increase in the proof stress and tensile strength. The following Table V shows the results obtained by such treatment when applied to the hot rolled bar examples previously shown in Table III.

As distinct from all other known alloys of this type the alloys according to this invention should on no account be subjected to a solution heat treatment after hot working unless the product is to be subjected to a subsequent cold working operation. Such a solution treatment of a hot worked product, even though followed by a precipitation heat treatment, cannot achieve a better combination of properties and frequently results in inferior properties to those which can be achieved according to this invention.

It will be obvious therefore that hot worked products produced according to this invention after finishing the hot working must be allowed to cool freely in air and must not be subjected to a more rapid rate of cooling, such as would be obtained by quenching in oil or water, since such treatment can only result in a reduction in the proof stress and hardness.

However, if the wrought products are inadvantently cooled more rapidly than desired, this would be immediately detected by a low result on hardness test and the required tensile properties could be readily achieved by subjecting the rapidly cooled wrought products to a precipitation hardening treatment as described above.

As stated above, hot worked products in alloys according to this invention do not require a solution heattreatment in order to achieve the required combination of properties.

However, a solution heat-treatment following a hot working operation is desirable if the product requires subsequent cold working. For this purpose hot rolled bar, forged slabs, hot rolled sheet, etc. should be solution heattreated by heating within the temperature range 750 C. to 1000 C. followed by rapid cooling in air, oil or water, when they will be in their softest condition and readily cold workable. After this cold working treatment the finished products which may be sheet, strip, rod, wire or cold extruded components, may be subjected to a further precipitation hardening treatment after which the products will possess extremely high tensile properties, combined with excellent ductility and Izod Impact Values. Table VI indicates typical properties obtained on rod TABLE V 0.1% Ultimate Proof Tensile Izod Example Ni, Al, Mn, Fe, Condition Stress, Strength, Elong., Impact Percent Percent Percent Percent Tons! Tons/ Percent Value, sq. in. sq. in. ttJlbs.

17.3 1.59 4.87 1. 14 Hot rolled bar precipitation hardening 4 43.0 56.0 20

hrs. at 550 C. 23. 8 1. 65 4. 4 0. 80 do 35. 8 57. 8 24 19.0 1. 75 4. 25 0. 80 36. 2 54. 4 22 32 29.2 1. 81 5.0 1.01 35. 2 53. 4 25 40 18. 2 1.86 4. 77 1.32 36. 6 54.8 22 37 17. 1 2. 22 5. 1. 11 43. 6 59. 6 16 16 19.5 2. 32 4. 1. 0 43. 6 59. 6 15 17 23.1 2. 37 4. 55 0.88 45. 6 63. 2 14 1O 27. 5 2.81 4. 55 0.95 50. 4 67. 2 9 4. 5

From Tables III and V it will be obvious that hot worked products showing the lowest proof stress in the hot worked condition exhibit the greatest response to which had been solution treated by heating to 920 C. quenched in water, cold drawn with various reductions in cross section as indicated in the table and finally precipiprecipitation hardening. tation hardened as stated in the table.

TABLE VI 0.1% Ultimate Izod Percent Reduction of Precipitation Proof Tensile Elongation, Reduction Impact area in cold drawing Hardening Stress, Strength, Percent in Area, Value, Treatment Tons/sq. Tons/sq. Percent ft./lbs.

inch inch 10 4 hrs. at 500 C 38 52 22 40 55 20 .do. 45 55 18 37. 5 55 3O 4 hrs. at 450 C 48 58 16 37. 5 55 50"- do 55 62 14 37.5 52 7O 4 hrs. at 425 C 53 65 11 27.5 44

Hot worked products showing a high proof stress in the hot Worked condition should not be subjected to precipitation hardening since this results in little increase in strength but appreciable reduction in elongation and Izod Impact Value.

This invention also envisages the use of other additional elements to enhance certain characteristics of these alloys and in particular, colurnbium, silicon, chromium and lithium have beneficial effects for special applications.

Columbium has the effect of developing a very high tensile strength combined with good ductility in hot low magnetic permeability by which We mean certainly worked products, see Table VII. less than 1.1 and preferably less than 1.05.

TABLE VII 0.1% Ultimate Izod Ni, Al, Mn, Fe, Cb, Proof Tensile Elong., Impact Example percent percent percent percent percent Condition Stress, Strength, percent Value, Tons/sq. Tons/sq. ft./1b.

inch inch 18.0 1.75 5.4 0.95 0.30 2 sq. hot rolled bar 34.0 52.8 23 35 18.0 1.75 5.4 0.95 0.30 2"sq. hot rolledbar+4 hrs. at 550C 38.0 55.0 20 15 18.0 1.75 5.4 005 030 1" sq. hotrolledbar 33.5 52.5 32 40 18.0 1.75 5.4 0. 95 0.30 1' sq. hot rolled bar+4 hrs. at 550 C 35.5 55 5 27 21 18.2 2. 80 4. 85 1.18 0.80 sq. hot rolled bar 49. 5 62. 2 24 19 18.2 2.80 4.85 1.18 0.80 4 sq. hot rolled bar+4 hrs. at 550 c 54.0 55.5 18 7 The addition of silicon to alloys according to this in- Magnetic permeability is a function of the nickel and vention also results in hot worked products possessing exiron contents, the iron being present in an amount of at tremely high proof stress and tensile strengths combined least 0.5% to perform a useful grain refining function. with good ductility. Such alloys also possess an excellent However, in a copper nickel alloy having a nickel conresistance to wear and abrasion. tent in the range 15 to 32% any significant addition of Examples of the properties which have been obtained iron beyond say, 6% reduces the corrosion resistance on hot rolled bar produced from alloys containing silicon properties of the alloy and it is preferred that the Without being subjected to further heat-treatment are nickelziron ratio should be as high as possible for any shown in Table VIII. given nickel content, and should not be less than 6:1.

TABLE VIII 0.1% Ultimate Proof Tensile Example Ni, Al, Mn, Fe, Si, Condition Stress, Strength, Elong., percent percent percent percent percent Tons/sq. Tons/sq. percent inch inch 17.9 2.79 5.15 1.01 0.77 sq. hot rolled bar 48.5 52.0 15.0 18.5 1.85 5.3 1.10 0.55 2%"sq. 43.5 59 5 19.5 18.5 1.85 5.3 1.10 0.55 1" sq. hotrolled abr 44.0 59 5 19.0

Chromium has little efliect on the tensile properties Moreover, in order to obtain in addition, the low magof the alloys according to this invention, but it is benenetic permeability values discussed above, it is necessary ficial in refining the grain size. to reduce the iron content still further and it has been Alloys according to the invention may also be profound that the desired values can only be obtained if the duced in the form of sand castings in which condition iron content is maintained below 3% and can only be they possess an excellent combination of properties as ensured, that is, taking into account reasonable manushown by the following example. facturing tolerances, if the iron content is maintained be- An alloy of the composition: low 2%. Accordingly the alloy provided by this inven- Percent tion and having a nickel content in the range 15% to Nickel 17.3 32%, has an iron content in the range 0.5% to 2% and Aluminium 1.96 indeed, such an alloy will usually be found to have a Manganese 5.15 magnetic permeability of less than 1.05. Iron 1.32 That the alloys provided according to this invention as described above, have low magnetic permeability is shown Balance substantially all copper, when cast into a sand by Examples 35 and 36 of Table IX Example 35 when mould possesses the following mechanical properties: produced in the form of a hot rolled bar possessed a Proof Stress (01%) "tons/Sq inch" 290 netic permeability of 1.01 while Example 36 when cast Tensile strength "tons/sq inch" 430 into a sand mould and Without further heat treatment, Elongation "percent" 13 possessed a magnetic permeability of 1.005. Izod Impact Value "ft. 28 Example 37 although having an acceptably low magnetic permeability would require very accurate control of It will be recalled that the object of the present inventhe nickel and iron contents for the value of 1.05 to be tion is to produce a high strength corrosion resistant copconsistently achieved, since as shown in Example 38, a per nickel alloy which is nonmagnetic and which has a comparatively small decrease in the nickel content-from nickel content in the range 15% to 32%. Such an al- 16% to 15.5 %coupled with a small increase in the iron loy is particularly required in marine engineering praccontentfrom 2.6% to 3.18%is accompanied by a sigtice, in which art, where a non-magnetic alloy of the kind nificant rise in the magnetic permeability value-of 1.05 in question is called for, an alloy having a magnetic in Example 37 to 1.3 in the case of Example 38. permeability in excess of 1.1 would be unacceptable. In- Examples 39 to 45 show how magnetic permeability deed, in this field, for many uses, a magnetic permeability values rise significantly with increases in the iron content, of 1.05 or more would be unacceptable. Accordingly, it of the nickel, aluminium and manganese contents of the is an object of this invention that the alloys should have alloy are maintained substantially constant.

TABLE IX Percent Percent Percent Percent Percent Magnetic Example Aluminium Nickel Manganese Iron Copper Condition Pgfieal. 55 16.9 5.3 0.88 Balance Wrought"... 1. 01 1.80 19.4 4.7 0.95 do Cast... 1. 81 15. 0 5. 5 2. 5 Wrought 1. 15. 5 4. 05 3.18 do 1. 71 17. 2 5. 15 5. 24 do 1. 55 15. 0 4.10 5. 2 do 1. 83 18.2 4. 7 5. 85 ..do 1. 5 17.5 4. 25 7. 72 do 1. 59 18. 2 4.7 8. 8 do.. 1.55 15.5 5.15 9. 22 .do do 1.75 15.0 4.85 5.35 -do Cast We claim:

1. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 25 tons per square inch, comprising:

Percent Nickel 15.0-32.0 Aluminium 1.5-3 .0 Manganese 4.0-6.0 Iron 0.52.0

the aluminium content being less than one-sixth of the nickel content, and the balance being substantially all copper.

2. An alloy as defined in claim 1, including at least one of the following elements in the following proportions:

Percent Chromium up to Columbium up to 3 Silicon up to 3 3. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 25 tons per square inch, comprising:

'Percent Nickel 15.0-25.0 Aluminium 1.5-2.1 Manganese 4.0-6.0 Iron 05-20 with the manganese content being less than one third of the nickel content and the aluminium content being less than one sixth of the nickel content, and the balance being substantially all copper.

4. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 35 tons per square inch, comprising:

Percent Nickel 15.0-25.0 Aluminium 2 3 Manganese 4 6 Iron 0.5-2.0

with the manganese content being less than one third of the nickel content and the aluminium content being less than one sixth of the nickel content and the balance being substantially all copper.

5. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 25 tons per square inch, comprising:

Percent Nickel 15.0-20.0 Aluminium 1.5-2.1 Manganese 4 5 Iron 0.5-1.5

Copper substantially the balance.

12 6. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 35 tons per square inch, comprising:

Percent Nickel 15.0-20.0 Aluminium 2.2-3 .0 Manganese 4.5-5.5 Iron 0.5-1.5

Copper substantially the balance.

with the manganese content being less than one third of the nickel content and the aluminium content being less than one sixth of the nickel content and the balance being substantially all copper.

7. A corrosion resistant high strength ductile copper nickel alloy with low magnetic permeability of less than 1.05 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 25 tons per square inch, comprising:

Percent Nickel 15-32 Aluminium 1.5-3 Manganese 4 5 Iron 0.5-2.0

Copper substantially the balance.

8. A corrosion resistant high strength ductile copper nickel alloy. with low magnetic permeability of less than 1.1 which after hot working and without the necessity of subsequent solution treatment or precipitation hardening, possesses a 0.1% proof stress of at least 25 tons per square inch, comprising:

Percent Nickel 1S-32 Aluminium 1.5-3 Manganese 4 6 Iron 0.5-2

Copper substantially the balance.

and including at least one of the following elements in the following proportions:

CHARLES N. LOVELL, Primary Examiner. 

